Seat arrangements providing adjustable lumbar support

ABSTRACT

A seat back comprises a frame structure from which are resiliently suspended a first platform element and a second platform element that together provide support for the upholstery of the seat. The first platform element can be buckled to provide adjustable horizontal lumbar support. In addition, the lower margin of the platform element is coupled to a cranked shaft that can be adjustably rotated to vary the vertical position of the platform element in the frame structure. During such adjustment, the upper margin of the platform element (3) slides upon lateral rails of the upper platform element (4).

This invention concerns improvements in and relating to seatarrangements providing adjustable lumbar support. Such an arrangement isparticularly adapted to a seat structure for use in an automobile, bus,minibus, train, office or furniture seat of the kind wherein a platformelement providing support for the upholstery of the seat is resilientlysuspended in a seat frame.

It is known, see for example EP 0 169 293, that an assembly forincorporation in a seat back to provide adjustable lumbar support maycomprise a platform element adapted to be suspended in a seat frame tosupport the cushioning of a seat rest, said platform element includingtwo elongate lateral rails between which extend transverse members thatprovide the platform support, adjustable means being linked betweenrespective portions of each of said elongate rails to apply thereto aforce of longitudinal compression, whereby said rails are caused to bearched outwardly in the lumbar region of the back rest together with thetransverse members carried thereby.

Such an arrangement provides an adjustable and comfortable lumbarsupport which is of relatively simple design. It has the disadvantage,however, that although the degree of lumbar support can be readilyadjusted in the horizontal direction, the vertical position at whichlumbar support is provided is determined by the initial geometric shapeof the platform element and the points at which the compression forcesare applied to the lateral rails, so that it is impossible for anoccupant of the seat to adjust the lumbar support in a verticaldirection to meet individual requirements.

Other systems are available to provide for vertical adjustment of lumbarsupport, but these have the disadvantage, either that they are notadaptable to the particular arrangement initially referred to or thatadjustment of the vertical and horizontal positions of the lumbarsupport are not fully independent of one another.

It is accordingly an object of the invention to provide, in a simplemanner, a novel construction of seat back that enables both horizontaland vertical adjustment of lumbar support.

The invention accordingly provides a seat back comprising a framestructure from which is resiliently suspended a platform element forsupporting upholstery of the seat, said platform element being linked toa first adjusting means for applying a force of longitudinal compressionbetween points of the platform element spaced in a vertical direction,in order to cause resilience buckling of the platform element to archoutwardly in the lumbar region of the back rest, and said platformelement being linked to a second adjusting means for effecting verticaldisplacement of said platform element relatively to the said framestructure.

Advantageously the said second adjusting means is coupled between theframe structure and a lower margin of the said platform element in sucha manner that the said lower margin is fixed in its vertically adjustedposition. Such an arrangement not only enables the construction of thesecond adjusting means to be mechanically simple, but also improves theeffectiveness of the horizontal lumbar adjustment, since it reduces thetendency of the resiliently suspended platform element to becomehorizontally displaced to a greater extent by load on the seat back,when the platform element is arched to provide greater lumbar support.

According to one embodiment of the invention, the platform elementproviding the adjustable lumbar support may be supplemented by a secondresiliently suspended platform element located in the upper region ofthe back rest, the arrangement being such that the further platformelement provides support for the upper horizontal margin of the firstplatform element, whilst accommodating relative sliding motion of thefirst platform element under the influence of the second adjustingmeans.

The platform element or platform elements may advantageously be of thekind comprising a wire grid, wherein transverse supporting wires aretensioned between lateral rails that are in turn coupled to the framestructure by tension springs.

Further preferred features and advantages of the invention will becomeapparent from the following description of one exemplary embodiment ofthe invention that is illustrated in the accompanying drawings, inwhich:

FIG. 1 is a front elevation of a back rest of a vehicle seatincorporating an arrangement in accordance with the invention,

FIG. 2 is a side elevation of a platform assembly of the arrangementillustrated in FIG. 1, and

FIG. 3 is an enlarged fragmentary view of a part of FIG. 2.

Referring to the drawings, the reference numeral 1 illustrates the frameof a seat back for an automobile seat. The seat is illustrated with theupholstery removed, and, suspended within the frame 1 by means oftension springs illustrated in broken lines at 2, are transverselyextending platform elements 3 and 4 that provide support for theupholstery of the seat.

In known manner each of the platform elements comprises a wire gridconsisting of lateral rails 5 or 6 formed by steel cords that arepaper-wrapped or coated with synthetic plastics material, between whichare tensioned transverse wires 7 or 8 penetrating intermediate tubes 9or 10 of synthetic plastics material. For clarity only one of thetransverse wires 7 or 8 are shown in full lines in the drawings, thepositions of the remaining wires being indicated in broken lines.

A sub frame 11 of formed wire is secured to the side rails 5 of theplatform element 3 by means of clips 12. The sub frame 11 is formed toinclude U-shaped loops 13, within which are anchored synthetic plasticsblocks 14 forming ferrules for the connection of a pair of Bowden cables15 and 16 respectively.

A further sub frame 17 of formed wire is anchored to the lower ends ofthe rails 5 of the platform element 3 by means of clips 18.

The Bowden cables 15 and 16 are linked to a common actuating mechanism19 mounted on the frame 1, and inner cables 15A and 16A of the Bowmencables 15 and 16 are anchored at their ends to hooked portions 17A ofthe sub frame 17.

A centre section 17B of the sub frame 17 forms a bottom rail for theplatform element 3 and is linked by means of clips 20 to a cranked shaft21, as indicated more clearly in FIG. 3. The shaft 21 is pivoted in theframe 1 about an axis 22 (FIG. 3) and can be pivoted to an arc indicatedby the arrow 23 in FIG. 3 via a lever 24 coupled to a manual actuatingmeans 25 located in the frame 1, by means of a connecting rod 26.

The upper ends of the two lateral rails 5 have portions 5A bent at rightangles and are clipped together by means of a clip 27 to form an upperhorizontal margin of the platform element 3. The lower ends of the rails6 are turned inwards at an acute angle at 6A and rest upon anappropriate transverse wire 8 in order to provide support for theportions 5A forming the upper margin of the platform element 3. Theupper ends of the rails 6 are hooked at 6B (FIG. 2) and engage inapertures in a flange (not illustrated) of the frame 1.

Upon actuation of the actuating means 19 to contract the Bowden cables15 and 16, the two sub frames 11 and 17 are drawn together by tensionexerted between the loops 14 and the hooked portions 17A, so that anintermediate portion 3A (FIG. 2) of the sub frame 3 is caused to archoutwardly in order to adjust the horizontal position of the lumbarsupport provided by the platform 3. Upon operation of the actuatingmeans 19 to relax the Bowden cables 15 and 16, the platform element 3will tend to return to its original condition, under the influence ofthe tension springs 2, its own inherent resilence, and load upon theseat.

By manual operation of the actuating means 25, the cranked shaft 21 canbe rotated to raise or lower the position of the lower margins 17B ofthe platform element 3. The vertical position of the lumbar supportprovided by the portion 3A of the platform element 3 can thus becorrespondingly adjusted. Vertical movement of the platform element 3 isaccommodated by corresponding movement of the tension springs 2 and byflexing of the Bowden cables 15 and 16. The upper margin of the platformelement 3 slides upon the rails 6,6A of the upper platform element 4,the, preferably, plastics coating of the steel cords serving to reducefriction and avoid the generation of noise.

It will be appreciated that the arrangement as described provides asimple and effective means of obtaining both horizontal and verticaladjustment of lumbar support. The fact that the platform element 3 isadjustably located in a fixed position at its lower margin 17B enables asimple lever actuated adjustment mechanism to be adopted whilst alsoproviding for positive location of the arched lumbar support in thehorizontal direction, so that the tendency for the lower edge of theplatform element 3 to be displaced under load is eliminated. Theprovision of the additional platform element 4,fixed at its upper end,avoids disturbance of the position of the upholstery in the uppersection of the seat back as the vertical position of the platformelement 3 is adjusted, whilst also enabling a more consistent springsuspension of the upper margin of the platform element 3 through avertical range of movement.

Various alterations and modifications may be made to the illustratedembodiment without departing from the scope of the invention. Thus,although separate manual actuating means 19 and 25 are illustrated forthe provision of horizontal and vertical lumbar support, the twocontrols could be combined in a single unit, for example as two-partknob, or in an electrically driven actuating means. Although theactuating means are illustrated as being mounted upon the frame 1, themanual controls may be remotely located at any desired position.

I claim:
 1. A seat back comprising a frame structure from which areresiliently suspended a first platform element for supporting upholsteryof the seat in a lower region of said seat back and a second platformelement for supporting upholstery of the seat in an upper region of saidseat back, said first platform element being linked to a first adjustingmeans for applying a force of longitudinal compression between points ofthe platform elements based in a vertical direction, in order to causeresilient buckling of the first platform to arch outwardly in the lumbarregion of the back rest, whereby lumbar support provided by said firstplatform element can be varied in a horizontal direction, and said firstplatform element is linked to a second adjusting means for effectingvertical displacement of said first platform element relative to thesaid frame structure, whereby lumbar support can be varied in a verticaldirection, an upper end of said first platform element slidably engagingover a lower end of said second platform element.
 2. A seat backaccording to claim 1 characterised in that said second adjusting meansis coupled between the frame structure and a lower margin of the saidfirst platform element.
 3. A seat back according to claim 2,characterised in that said second adjusting means comprises a shaftjournalled at its ends in the frame structure and having an eccentricintermediate portion pivotally coupled to said lower margin of the saidfirst platform element.
 4. A seat back according to claim 3, wherein theplatform element comprises a wire grid, wherein transfer supportingwires are tensioned between lateral rails that are coupled to the framestructure by tension springs.
 5. A seat back according to claim 4,wherein the platform element has lateral rails and an upper margin, thelateral rails being interconnected at their upper ends to form atransverse rail at the upper margin of the platform element that canslide against lateral rails of a second platform element.
 6. A seat backaccording to claim 5, wherein the lateral rails of the second platformelement have obliquely angled interned ends to provide additionalsupport for said transverse rail.
 7. A seat back according to claim 1,characterised in that the platform elements each comprise a wire grid,wherein transverse supporting wires are tensioned between lateral railsthat are in turn coupled to the frame structure by tension springs.
 8. Aseat back according to claim 7, characterised in that the lateral railsof the first platform element are interconnected at their upper ends toform a transverse rail at the upper margin of the platform element thatcan slide against the lateral rails of the second platform element.
 9. Aseat back according to claim 8, characterised in that the lateral railsof the second platform element have obliquely angled inturned ends toprovide additional support for the transverse rail of the first platformelement.
 10. A seat back having a lumbar region and comprising a framestructure from which is resiliently suspended a platform element forsupporting upholstery of the seat, said platform element being linked toa first adjusting means for applying a force of longitudinal compressionbetween points of the platform element spaced in a vertical direction,in order to cause resilient buckling of the platform element to archoutwardly in the lumbar region, said platform element being linked to asecond adjusting means for effecting vertical displacement of saidplatform element relative to said frame structure, the second adjustingmeans being coupled between the frame structure and a lower margin ofsaid platform element, comprising a shaft journaled at its ends in theframe structure and having an eccentric intermediate portion pivotallycoupled to said lower margin of said platform element.